The present invention relates to a communicating method between a master and a slave connected through a belt connected to a gripper-unit in a hoist device of a rail car, and to technology in which the master and the slave perform power line communication through a power supply line for supplying power formed in a belt, thereby more stably transmitting and receiving signals in a simple system structure.
Generally, in manufacturing processes of a semiconductor element and a liquid crystal display device etc., the manufacturing goods are transferred to the manufacturing equipment of each manufacturing process by using an automated material handling system (AMHS), so that the corresponding goods are manufactured according to the manufacturing processes of each manufacturing equipment. Such an automated material handling system utilizes a rail car for transferring a carrier of receiving a semiconductor substrate or a liquid crystal substrate to the manufacturing station located on the manufacturing process line and transferring the carrier of again receiving the goods completely processed in the corresponding manufacturing equipment to the next manufacturing equipment.
Depending on the movement method thereof, the rail car includes an automated rail car (AGV) for driving through the wheel, a rail guided vehicle (RGV) for driving along the guide rail located at the bottom, and an overhead hoist transport (OHT) for driving a guide rail installed in the ceiling. These unmanned transporting devices are moved to the corresponding manufacturing equipment by using the wheel itself or along the bottom rail or the overhead rail and it carries the carrier onto or carries the carrier out the manufacturing equipment by using an operating arm or a hoist and a gripper.
FIG. 1 is a diagram for explaining a configuration of a rail car in a conventional automated material handling system and shows a process of carrying out a hoist operation of the rail car. As shown in FIG. 1, (A) is a stage in which the rail car 10 having a carrier (3) moves to a position of the manufacturing equipment (2) along a rail (1), (B) is a stage in which the carrier (3) is placed on the manufacturing equipment (2) by descending a belt (12) by means of the rail car (10), and (C) is a stage in which the rail car (10) lifts the belt (12) while placing the carrier (3) in the manufacturing equipment (2) so as to perform the corresponding process operation on the carrier (3) in the manufacturing equipment (2).
Referring to FIG. 1, the rail car (10) includes a hoist (11), a belt (12), and a gripper unit (13).
When the rail car (10) is located to the manufacturing equipment (2) by moving it along the rail (1), the rail car (10) allows the gripper unit (13) to move up and down by means of the belt 12, so that it carries the carrier (3) onto or carries the carrier (3) out the manufacturing equipment (2).
At this time, the hoist (11) includes a master controller (not shown) on the upper side of the belt (12) and a slave controller (not shown) on the lower side of the belt (12), that is, on a side of the gripper unit (13) and a power supply line and a communication line are formed on the belt (12), so that it provides the power and transmits and receives information related to the gripper operation between the controller of the rail car and the controller of the gripper unit.
That is, the hoist (11) provides the control signal for hoist operation to the slave communication unit via the belt (12) in the master communication unit and provides the control signal related to the hoist operation to the gripper unit (13) in the slave communication unit, so that it can perform the actual operations of moving the gripper unit (13) in a fastened state of the carrier (3) or placing the carrier 3 on the manufacturing equipment 2 and so on.
At this time, the conventional hoist (11) is configured to perform the communication between the master communication unit and the slave communication unit by providing a conductive line for power supply and a conductive line for communication inside the belt, respectively. However, it is a cumbersome to form the conductive lines in the belt.
Further, in the case of the rail car having a structure in which the belt is lifted and lowered in the manner of a normal slip ring, there is a problem of a contact failure due to a contamination, a deformation, a friction etc. of the slip ring or the brush.
Accordingly, where the serial communication is performed using the conductive lines formed on the belt, since the noise is generated in the transmitting and receiving data, there is a problem in that it is difficult to secure reliability of data transmitted and received through the belt.
Thus, it has been proposed a method of performing an optical communication between a body of the rail car and a lifting and descending rigid body in the structure of lifting and descending the belt by the slip ring manner. However, a communication error can occur due to an optical noise interference with the other rail car located in the periphery thereof. Also, there is a problem that the optical communication is interrupted, when the gripper unit is vibrated in all directions.
In addition, since the optical communication generally has a low communication speed and has a limitation in increasing the number of data bits, there is a disadvantage in that the expandability of additional functions such as a collision detection, a vibration detection, a power management etc. can be deteriorated.